Children with growth retardation (greater that -2 standard deviation score) post renal transplantation will be enrolled in a multi-center, randomized trial of recombinant human growth hormone (rhGH) to determine its effect on growth and on the development or progression of acute and chronic rejection. A kidney biopsy will be performed before starting rhGH to assess the presence of chronic rejection. Growth hormone will be given for 30 months. A control group will wait for one year after randomization before starting rhGH therapy.